15.2-EvidenceofEvolution

The theory of evolution states that all organisms on Earth have descended from a single ancestor.! !Recall that theories provide explanations for natural phenomena based on observation.!Ex: cell theory, heliocentric theory, theory of plate tectonics!

Evidence for evolution comes from:• The fossil record!• Comparative anatomy!• Comparative embryology!• Comparative biochemistry!• Geographic distribution !

The fossil record is an important source of information for determining the ancestry of organisms and the patterns of evolution.!

•  shows how modern species resemble ancient species!•  shows that some species have

changed very little. !

The glyptodont was an ancient ancestor of the modern armadillo.!

Darwin predicted the existence of intermediate organisms, or transitional fossils between species, such as Archaeopteryx!

2 types of traits :• Derived traits newly evolved features that aren’t in the fossils of common ancestors.!• Ancestral traits features that do appear in ancestral forms.!

Comparative anatomyEvolutionary Theory predicts body parts are more likely to be modified from ancestral body parts than entirely new structures. !

homologous structures similar structures inherited from a common ancestor!

Evolutionary theory predicts features that no longer have a use will become smaller over time until they are lost. !

Vestigial structures reduced forms of functional structures!

snake pelvis! human appendix!

Body parts with similar functions can evolve independently under similar conditions. !!

Analogous structures serve the same purpose, but are not inherited from a common ancestor!

Comparative embryologyEmbryo- an early, pre-birth stage of an organism’s development. !!Vertebrate embryos have homologous structures during development that become totally different structures in the adult forms.!

Comparative biochemistryCommon ancestry can be seen in the complex metabolic molecules that many different organisms share.!

• The more closely related species are to each other, the greater the biochemical similarity. !

Geographic distributionBiogeography- study of the distribution of plants and animals around the world!•  Evolution is linked to migration

patterns, climate, and geological forces (such as plate tectonics). !

Adaptation a trait that increases an organism’s ability to survive!Fitness ability of an organism to survive and reproduce.!!The better an organism is adapted to its environment, the greater its chances of survival and reproductive success. !

Types of adaptations•  Camouflage adaptation that allows

an organism to blend into its environment. !•  Mimicry adaptation where a species

resembles another species. !•  Antimicrobial resistance develops in

some bacteria in response to exposure to antibiotics. !